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https://github.com/RGBCube/serenity
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LibGfx: Decode paletted and grayscale images with 1/2/4 bit depth
When dealing with png data that has less than 8 bits per pixel, round up to the next byte when allocating per row buffers and streamers. This fixes decoding odd sized PNGs with less than 8 bits per pixel. Also added a test page with some odd sized palleted PNGs.
This commit is contained in:
LepkoQQ
Andreas Kling
parent
e37065cc8b
commit
c7f0de14b5
3 changed files with 95 additions and 32 deletions
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@ -30,6 +30,7 @@
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#include <AK/NetworkOrdered.h>
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#include <LibCore/puff.h>
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#include <LibGfx/PNGLoader.h>
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#include <LibM/math.h>
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#include <fcntl.h>
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#include <serenity.h>
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#include <stdio.h>
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@ -120,7 +121,7 @@ struct PNGLoadingContext {
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u8 compression_method { 0 };
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u8 filter_method { 0 };
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u8 interlace_method { 0 };
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u8 bytes_per_pixel { 0 };
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u8 channels { 0 };
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bool has_seen_zlib_header { false };
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bool has_alpha() const { return color_type & 4 || palette_transparency_data.size() > 0; }
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Vector<Scanline> scanlines;
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@ -339,6 +340,21 @@ NEVER_INLINE FLATTEN static void unfilter(PNGLoadingContext& context)
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pixel.a = 0xff;
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}
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}
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} else if (context.bit_depth == 1 || context.bit_depth == 2 || context.bit_depth == 4) {
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auto pixels_per_byte = 8 / context.bit_depth;
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auto mask = (1 << context.bit_depth) - 1;
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for (int y = 0; y < context.height; ++y) {
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auto* gray_values = (u8*)context.scanlines[y].data.data();
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for (int i = 0; i < context.width; ++i) {
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auto bit_offset = (8 - context.bit_depth) - (context.bit_depth * (i % pixels_per_byte));
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auto value = (gray_values[i / pixels_per_byte] >> bit_offset) & mask;
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auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
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pixel.r = value * (0xff / pow(context.bit_depth, 2));
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pixel.g = value * (0xff / pow(context.bit_depth, 2));
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pixel.b = value * (0xff / pow(context.bit_depth, 2));
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pixel.a = 0xff;
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}
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}
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} else {
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ASSERT_NOT_REACHED();
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}
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@ -418,19 +434,42 @@ NEVER_INLINE FLATTEN static void unfilter(PNGLoadingContext& context)
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}
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break;
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case 3:
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for (int y = 0; y < context.height; ++y) {
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auto* palette_index = (u8*)context.scanlines[y].data.data();
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for (int i = 0; i < context.width; ++i) {
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auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
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auto& color = context.palette_data.at((int)palette_index[i]);
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auto transparency = context.palette_transparency_data.size() >= palette_index[i] + 1u
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? context.palette_transparency_data.data()[palette_index[i]]
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: 0xff;
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pixel.r = color.r;
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pixel.g = color.g;
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pixel.b = color.b;
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pixel.a = transparency;
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if (context.bit_depth == 8) {
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for (int y = 0; y < context.height; ++y) {
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auto* palette_index = (u8*)context.scanlines[y].data.data();
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for (int i = 0; i < context.width; ++i) {
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auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
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auto& color = context.palette_data.at((int)palette_index[i]);
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auto transparency = context.palette_transparency_data.size() >= palette_index[i] + 1u
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? context.palette_transparency_data.data()[palette_index[i]]
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: 0xff;
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pixel.r = color.r;
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pixel.g = color.g;
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pixel.b = color.b;
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pixel.a = transparency;
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}
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}
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} else if (context.bit_depth == 1 || context.bit_depth == 2 || context.bit_depth == 4) {
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auto pixels_per_byte = 8 / context.bit_depth;
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auto mask = (1 << context.bit_depth) - 1;
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for (int y = 0; y < context.height; ++y) {
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auto* palette_indexes = (u8*)context.scanlines[y].data.data();
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for (int i = 0; i < context.width; ++i) {
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auto bit_offset = (8 - context.bit_depth) - (context.bit_depth * (i % pixels_per_byte));
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auto palette_index = (palette_indexes[i / pixels_per_byte] >> bit_offset) & mask;
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auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
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auto& color = context.palette_data.at(palette_index);
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auto transparency = context.palette_transparency_data.size() >= palette_index + 1u
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? context.palette_transparency_data.data()[palette_index]
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: 0xff;
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pixel.r = color.r;
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pixel.g = color.g;
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pixel.b = color.b;
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pixel.a = transparency;
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}
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}
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} else {
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ASSERT_NOT_REACHED();
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}
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break;
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default:
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@ -586,7 +625,8 @@ static bool decode_png_bitmap(PNGLoadingContext& context)
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context.scanlines.append({ filter });
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auto& scanline_buffer = context.scanlines.last().data;
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if (!streamer.wrap_bytes(scanline_buffer, context.width * context.bytes_per_pixel)) {
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auto row_size = ((context.width * context.channels * context.bit_depth) + 7) / 8;
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if (!streamer.wrap_bytes(scanline_buffer, row_size)) {
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context.state = PNGLoadingContext::State::Error;
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return false;
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}
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@ -648,36 +688,28 @@ static bool process_IHDR(const ByteBuffer& data, PNGLoadingContext& context, boo
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switch (context.color_type) {
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case 0: // Each pixel is a grayscale sample.
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// FIXME: Implement support for 1/2/4 bit grayscale based images.
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if (ihdr.bit_depth != 8 && ihdr.bit_depth != 16) {
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dbgprintf("PNGLoader::process_IHDR: Unsupported grayscale format (%d bpp).\n", context.bit_depth);
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return false;
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}
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context.bytes_per_pixel = ihdr.bit_depth / 8;
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context.channels = 1;
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break;
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case 4: // Each pixel is a grayscale sample, followed by an alpha sample.
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context.bytes_per_pixel = 2 * ihdr.bit_depth / 8;
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context.channels = 2;
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break;
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case 2:
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context.bytes_per_pixel = 3 * (ihdr.bit_depth / 8);
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case 2: // Each pixel is an RGB sample
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context.channels = 3;
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break;
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case 3: // Each pixel is a palette index; a PLTE chunk must appear.
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// FIXME: Implement support for 1/2/4 bit palette based images.
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if (ihdr.bit_depth != 8) {
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dbgprintf("PNGLoader::process_IHDR: Unsupported index-based format (%d bpp).\n", context.bit_depth);
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return false;
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}
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context.bytes_per_pixel = 1;
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context.channels = 1;
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break;
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case 6:
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context.bytes_per_pixel = 4 * (ihdr.bit_depth / 8);
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case 6: // Each pixel is an RGB sample, followed by an alpha sample.
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context.channels = 4;
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break;
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default:
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ASSERT_NOT_REACHED();
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}
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if (!decode_size_only) {
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context.decompression_buffer_size = (context.width * context.height * context.bytes_per_pixel + context.height);
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// Calculate number of bytes per row (+1 for filter)
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auto row_size = ((context.width * context.channels * context.bit_depth) + 7) / 8 + 1;
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context.decompression_buffer_size = row_size * context.height;
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context.decompression_buffer = (u8*)mmap_with_name(nullptr, context.decompression_buffer_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0, "PNG decompression buffer");
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}
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return true;
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